I was having the same problem with mine. Here's what it was. My intake valves were getting pretty gunked up over the years and causing high compression in the cylinders which caused my timing to change and cause spark knock. To avoid having to take the heads off you can try this first. (worked for me) let the engine warm up, then take your air cleaner off the throttle body. Get you a bottle of sea foam or you can use methanol (windshield washer fluid) and pull the throttle open to about 2000 - 2500 RPM's and slowly pour it in the intake. I prefer methanol as it's cheaper for how much you're getting. I slowly poured the whole gallon through my intake and suprise! No more knock and throttle response improved back to where it should because the compression went back down and the timing corrected itself.

 

deleted!

 

I have another thread going about this problem.. I was hearing a pinging noise/clatter of some sort...

I took a small ball pein hammer and started tapping stuff underneath the truck.. ended up figuring out that this transmission brace was cracked and would make a noise that sounded alot like pinging



you should check yours just for piece of mind.. hope this helps

later

 

Thanks for the replies everyone. Looks like I'll be crawling all over much truck again this weekend.

PressB, I already responded to the post you had in the "ghost pinging" thread, but I'm still amazed that this would work. Anyone else try this with success?

 

The thing about this is that you're not flooding the intake so that it's not getting any air. You pour slowly, like you're filling your radiator with antifreeze. It boils before it can bog it down. And since it's methanol it won't hurt anything. you can do the same with just water, however it doesn't work as good because it boils too fast and cools the valve down faster so it doesn't get as much carbon off as washer fluid. I promise, try it and you'll be amazed. I've done this on a couple of cars now that I know how well it works.

 

zman17, I did the vacuum test according the the link you posted, but I'm still confused about how to read the gauge. As soon as I start the truck, the needle drops at a pretty fast rate (past 20 inches in under 15 seconds). Does this mean I have a leak? I was a little confused by the instructions.

On a related note, what would happen (hypothetically of course) if the object I was using to plug the PCV valve port was sucked inside the intake manifold?

 

Probably something bad. I discovered by accident that a (fired) 300 WSM cartridge casing fits the PVC hole and line perfectly. No chance of it getting sucked in and perfect seal (perfect enough for our uses).

 

Does anyone know how I'm supposed to read the gauge?

 

have you went back and check #8 plug again? while its running you can also unplug #8 injector and see if the rpms change, if not, then bad injector

 

What do you mean the needle drops? It should be at zero and go into the negative side.(if the plenum gasket is ok) Not go up to 20 then drop.


Try this, it's better IMO. Pull the hose off the intake manifold from the PCV , and plug the hose and the barb on the intake it connects to. Then pull the hose off the air cleaner that goes to the 90 degree elbow on the opposite side and plug the hose. Then pull the dipstick and connect the the gauge to the dipstick tube. If you only have a vacuum gauge it will start at zero, what you want to see is the needle try to go in reverse. Not go up and give you a vacuum reading.